The kinetics of hybridization of labeled complementary DNA (cDNA) with complementary and heterologous poly(A) ion mRNA is being used to measure the distribution and abundance of mRNA sequences during the course of meiosis of yeast. A similar approach is being used to identify sequences which are unique to meiotic cells. Meiotic mutants and asporogenic diploids homozygous for one of the mating type alleles are being used to study the regulation of transcription in cells which are incompetent to undergo sexual reproduction when confronted with an environment that induces meiosis in competent cells. Cell surface proteins of vegetative cells and ascospores are being examined to determine whether there are proteins associated with ascospores that are synthesized only during meiosis and sporulation.